Cathode beam tube and circuit therefor



IN VEN TOR.

Hrm/w52 R. L. SNYDER, JR

Filed June 20, 1945 GATHODE BEAM TUBEV AND CIRCUIT THEREFOR Nov. 23, 1948.4

`in which:

Patented Nov. 23, 1948 Y f: t' f CATHoDE BEAM TUBE AND CIRCUIT i 'rHEREFoa Richard L. Snyder, Jr., Princeton, N. J., assignor to RadoCorporation of America, a corporation of Delaware Application June 20, 1945, Serial No. 600,498

There are various uses for cathode beam tubes capable of storing received signals, such as 1n radars, frequency reducers andother devices.

An object of the invention is to provide a cathode beam tube and circuit that will store signals for a predetermined number of scanning cycles on a dielectric target before utilization thereof.

Another object is to provide a cathode beam tube in which signals are stored on a dielectric target during one scanning cycle and utilized in the next.

`Another object is to provide a cathode beam tube in which signals are recorded on a dielectric target during one scansion by the beam and discharged therefrom on the next scansion by varying the relative potentials of screens positioned adjacent the target.

Other objects will appear in the following description, reference being had to the drawing,

The single figure of the drawing is a diagrammatic illustration of my storage tube and circuits therefor.

I Referring to the drawings, the storage tube I of my invention has an evacuated envelope 2 surrounded by a coil 3 for magnetic focusing of the electrons. Storage tube I has a cathode 4 with heater 5, surrounded by control grid 6 having the usual orice for controlling the cathode beam l. In front of the grid is the cylindrical anode 3 having an apertured `wall `8a for passage of the beam 1. The target 9 is secured by any means at the `front end of the envelope 2. This target may be round, square, or any other desired shape. It preferably consists of a thin sheet of mica, though other dielectric materials may be used. A signal plate I is positioned against the side of the target remote from the gun. On the gun side is positioned a shield screen II spaced a few millimeters therefrom. This is joined to wall coating I2, which is con- `nected to cylindrical anode 8. Closely adjacent the screen II on the gun side is placed control screen I3. Screens II and I3 may have the general configuration `of target 9.

elds perpendicular to the beam 1 and to each other.

The cathode 4 may be` connected to the vnegative 1,000 volt terminal of a power unit and the control grid to the cathode through a suitable negative bias source and an appropriatefresist- Inside the` fo- L cusing field and outside of the envelope 2 are to the drop in resistance 23.

7 claims. (Cl. 315-12) ance I5. The anode 8 may be connected to the positive ground terminal. The control screen I3` is connected so as to have a potential alternately negative and` positive relative to shield screen I I to control the escape of secondary electrons from the target.

The saw-'tooth generator I6 is connected to the horizontal deflector coil of unit I4'to provide the varying electromagnetic field for horizontal scansion by beam l. 'I'he vertical deector coil of this unit is connected to a constant direct current voltage source to position the beam in the `desired horizontal plane.

To record or storethe signals of one scanning cycleon target 9 and discharge them in another cycle, 'I employ a polarity reverser, designated in general by reference character I'I. This comprises a blocked type of multivibrator in which two tubes I8, I9, having plates and grids crosscoupled, are so biased that only one tube can be conducting at a time. Furthermore, the bias is such-that when one tube is conducting and the otheris not,` the condition will be stable if no interference is present. However, if a sharp negative pulse is applied to the connection 20 common to theplates of the tubes, the condition of the two tubes will reverse; that it, the tube originally non-conducting then conducts and vice versa. Such a pulse is obtained by coupling the saw-tooth generator I6 to the grid of the input lamplifier 2| through condenser 22 and connecting the plate of the amplifier to the lead 20 of the polarity reverser. When the pulse is produced, the voltage at both plates is lowered, due If, for example, tube I9 be assumed as previously non-conducting,

`the condenser 24 will discharge down to the lowered voltage through the 'resistance 25 in the grid circuit lof tube I8. Since the drop in this resistance is negatively applied, tube I8 blocks and tube I9 conducts. Upon occurrenceof the next pulse, condenser 26 will discharge through resistance 2l and reverse the condition. Thus, upon production of one pulse by a positive peak of saw-tooth generator I6, the plate of tube I8 willbe positive with respect to the plate of tube I9 and uponproduction of a pulse in the next cycle, the polarity will reverse.

I A pentagrid tube 28 is .used to impress the re- 'ceivedsignals on cathode beam l. Accordingly, the first control grid of this tube is connectedto the signalline 29 and the cathode is grounded throughcathode Ybias resistor 30; The blocking condenser 3| connects the second control grid of -this :tube to .the-polarity reverser to shut oifthe input signal to the storage tube during the reproducing cycle and turn it'on during the recording cycle, as later explained in more detail.

The plate of tube 28 is connected to the positive terminal of a B supply source through resistance 32. The various other terminals of tubes I8, I9, 2l and 28 are connected to appropriate voltage terminals and need not be de,- scribed. The plate terminal of tube 28 is coupled through condenser 33 to grid 6 of cathode beam tube I.

The condenser 22 is connected through resiste. ance 34 and negative bias source 35 to the cathode of tube 2 I, which is grounded. The high side of resistance 34 is connected to the grid of a blanking tube 36, which has its output circuit connected between the plate of tube 28 and ground. The grids of tubes 2I and 36 are biased by source 35 well below cut-off. The ground of tubes I8, I9, 2|, 28 and 36 may be the minus terminal of the B source, .or sources.

The plate of tube I3 is connected through condenser 3'! and resistance 38 to ground and the high end of resistance 38 is connected to control screen I3.

Suppose the saw-tooth generator I5 makes tube I9 of the polarity reverser I'I non-conducting as it causes the beam 'I to `sweep across the target 9. The potential at the plate of tube I9 4rises `and turns on amplifier 23. The signals coming in .over line 29 modulate the beam 'I'. Simultaneously with the reversal of polarity, the voltage of screen I3 becomes negative by virtue .of its coupling to the plate of .the conducting tube I8 through the large condenser 3l in conjunction with the high resistance 3 8. Thus, las the beam l sweeps across the target in this cycle, the secondary electrons bombarded from the target pass through screen II but are driven baCk there.- through and to the target because of the relative negative potential of screen I3, Due tothe focus.- ing action of the axial eld of coil 3, these return substantially to the spots from which thexr Were emitted. The electrons landed from the beam thus drive the scanned line of the dielectric surface varyingly negative in accordance with the signal. On the next cycle of the saw-.tooth een" erator, tube I8 blocks and tube i9 conducts. This blocks tube 28 and prevents the signals from modulating beam l. The rise of potential at the plate of tube I8 raises the potential of control screen I3 above the potential of shield screen I I, which is above the potentials of dielectric target 9, and the secondary electrons bombarded therefrom by the beam are drawn through both screens I I and I3 and are collected by anode wall 18a.

The ,electron velocity of the beam is such that the ratio of emission Vof secondary electrons to primary electrons is greater than unity; that is, more electrons leave the bombarded element of the target than are landed from' the beam. Hence, the elemental areas become positive. The copious emission of secondary electrons is ,such that this scansion of the beam raises all of the scanned areas of the target up to the potential of shield screen I;I, as no secondary electrons can pass through the shield screen should the target element under bombardment become more posi tive than the shield screen. This action of .the beam in the second scansion causes displacement currents to ilow in the elemental condensers formed by the surface of ythe dielectric under bombardment and the signal plate. These cur,- rents flowing through the output-resistor 5.0 .produce potential changes in. succession .on the sig v desired way through conductor 39, such as a synchronously operating oscilloscope.

The invention is not limited to putting signals on the plate in alternate scansions of the beam, as the use ,of suitable known counting devices may provide other scoring procedure and various other modifications may be made without departing from the scope of the invention.

Having described my invention, what I claim is:

1. A signal storage system comprising a cathode beam tube having a gun, a signal plate having a dielectric target surface facing said gun, a screen having one of its sides adjacent to and facing said dielectric target surface, and a second screen adjacent to and facing the other .Side of. the hrst screen. means for ,scaehihs the beam of. Said over said surface through Said Screen. a potential source ,for makihe the .first .streeh positive in respect t0 the .cathode .of .Said ehh and a .spighe of alternating potential for malghe the Seche@ screen positive in respect to the first screen in one lscansion o f the beam over nsaid surface and nega-tive thereto another scansion thereof.

.2. A signal .storage ,System comprising a Cathode beam tube having a gun, a dielectric target posihoned with one ,of its Sides fahne Sad ehh.. a screen having one of its sides adjacent to and facing said side of the target. and .a second ,Screen adjacent to and facing the other side of the .first screen, means fer making the first screen positive in respect to the cathode, means for scanning the cathode beam over said target, Said beam having suilcient electron velocity to produce secondary electrons from the target Whose ratio to primary electrons is greater than unity `and a source of alternating potential for making the second screen positive in respect to the ,first screen in .one `scansion of thev beam over said target and negati-ve thereto in another scansion.

v3. A signal storage system I,comprising aeathode beam tube havin-e a euri, and a `dieletri target positioned with .one Side .facing the gun, means for scanning a modulated beam over said target with vsufficient electron velocity to produce siec- .ondary electrons from the target whose ratio to primary electrons l is greater than unity and a control electrode in said .tube and a source of alternating potential applied to said electrode to cause it to attract secondary electrons from the target .during one scansion of the beam thereover and to repel them back to the target in another scansion thereof.

e. A signal storage system comprising .a cathode beam .tube having a gun, a dielectric target posi.- tioned with one of its sides facing the gun, and a screen having one ,of Aits sides adjacent to and facing said side of the target, means forscanning a modulated beam over said target through said screen with sufficient electron velocity to produce secondary electrons yfrom the target whose ratio :to pri-mary electrons. is greater than unity and .a source of alternating potential .connected to said screen to .cause :it to attract secondary electrons from .the target in alternate scahsohs 0f the beam.

5. A signal `storage system .comprising a ,cathod beam .tube having a gun, a dielectric .target posi.- tioned with one of its .Sides -aihe .the euh, .a screen having one of its, Sides :adjacent i0 .and

facing said side of the target, a signal plate on the other side of the target, means for scanning a modulated beam over said target through said screen with sufficient electron velocity to produce greater than unity electron emission from the target and a source of alternating potential connected between said screen and said signal plate to attract emitted electrons from the target during one scansion of the beam and to repel electrons back to the target in another scansion thereof.

6. A signal storage system comprising a cathode beam tube having a gun, a dielectric target positioned with one of its sides facing the gun, a screen having one of its sides adjacent to and facing the other side of the target, a second screen adjacent to and facing the other side of the first screen, a signal plate on the other side of the target, means for making the rst screen positive in relation to the cathode of said gun, a saw tooth generator, means connected to said saw tooth generator for scanning the cathode beam over said target through said screens said beam having sufficient electron velocity to produce electron emission from said target greater than unity and a multivibrator controlled by said saw tooth generator for making the second screen alternatively positive and negative in respect to the 'rst screen at alternate scansions of said beam over the target.

'T'. A signal storage system comprising a cathode beam tube having a gun, a dielectric target positioned With one of its sides facing the gun, a screen having one of its sidesadjacent to and facing said side of the target, a second screen adjacent to and facing the other side of the irst screen, a signal plate on the other side of the target, means 'for making the rst screen positive in relation to the cathode of said gun, means for scanning the beam of said gun over said target and means for making the second screen alternatively positive and negative in respect to the first screen at a rate proportional to the rate of the scansion of said beam over the target.

RICHARD L. SNYDER, J R.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STA'I'ES PATENTS Number Name Date 2,301,743 Nagy et al Nov. 10, 1942 FOREIGN PATENTS Number Country 4 Date 504,268 Great Britain Apr. 1'7, 1939 

